Penicillamine, a mercaptoamino acid, is a chelating drug used to treat Wilson's Disease and several disorders resulting from defects in the structure of connective tissue such as scleroderma, fibrosis, and rheumatoid arthritis. These diseases are associated with abnormalities in the biometabolism of copper. Characterization of copper complexes with penicillamine and related ligands is essential to (a) understanding how the drug mobilizes body copper stores and promotes their excretion; (b) designing more effective chemotherapies; and (c) possibly illuminating the biochemical nature of these diseases. Related model Zn(II) and Cd(II) mercaptide complexes also will be prepared and studied as models for the metal ion sites in metallothionens, proteins involved in the absorption, distribution, and storage of copper, zinc, and cadmium. Finally, various Cu(II)-mercaptide complexes will be prepared in attempts to model the chromophore of the blue copper proteins.